JPH0626004B2 - Magnetic recording and reproducing apparatus for digital video signals - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a magnetic recording / reproducing apparatus for a digital video signal, and more particularly, to a recording time for magnetically recording a video signal by converting it into a digital signal. The present invention relates to a magnetic recording and reproducing apparatus for magnetic recording of a digital video signal suitable for a long time.

[Background of the Invention]

As described in Delevision Society Journal, Vol. 34, No. 3, pages 213 to 220, the conventional digital video signal recording / reproducing apparatus (hereinafter referred to as a digital VTR) expands the recording band by a helical scan type. In order to achieve this, the number of rotations of the cylinder is increased, and at the same time, a plurality of heads are simultaneously recorded, and normally one field of information is composed of about 4 to 10 tracks.

A PCM method has also been proposed to reduce the bandwidth of digital information.

However, when the above conventional technique is used for a general home VTR, the recording time is reduced to about 1/4 to 1/10. Therefore, in order to record TV programs at home, the current VH
Since it requires 4 to 10 times as many recording tapes as those called the S method and the beta method, there is a problem that the economic efficiency is extremely poor.

[Object of the Invention]

The present invention has been made to eliminate the above-mentioned problems, and its purpose has not been considered in the prior art of the digital VTR. An object of the present invention is to provide a recording apparatus for a digital video signal, which secures both a digital information recording band and recording for a long time.

[Outline of Invention]

In order to achieve the above-mentioned object, in the present invention, in order to secure a recording band of a digital video signal, the number of rotations of a cylinder and the number of heads are kept as they are in the prior art, and the adjacent tracks are different from each other. Modulate digital information so that it becomes a frequency spectrum signal, record the adjacent tracks with azimuth angle difference in the recording head, and configure the recording pattern so that the tracks recorded on the tape are in contact with each other. There is a feature in the point.

Example of Invention

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, 1 is an input terminal for a color video signal, and 2 is an AG for making the level of a luminance signal input to the input terminal 1 constant.
C circuit, 3 is a separation circuit for separating the output of the AGC circuit 2 into a luminance signal and a carrier color signal, 4 is an ACC circuit for making the level of the burst signal included in the carrier color signal constant, and 5 is a carrier color signal Of the two color difference signals, for example, (B-
It is a color demodulation circuit that generates a Y) signal and an (RY) signal.

Reference numerals 6, 7, and 8 are low-pass filters (hereinafter abbreviated as LPF) for preventing return noise generated by an analog-digital converter (hereinafter abbreviated as AD converter), 9, 10, 11
Is an AD converter as the first conversion means for converting the analog signals output from the low-pass filters 6, 7, and 8 into digital signals.

Reference numeral 12 is a parallel-serial converter (hereinafter abbreviated as P → S converter) that outputs digital information (hereinafter referred to as data) input in parallel from the AD converters 10 and 11 as serial data, and 13 and 14 are AD converters 9. , P-S converter 1
This is a data processing circuit that inputs the output of 2 and adds the data necessary for error correction and rearranges the data.

Reference numeral 15 is a modulator as a first modulating means for modulating the output data of the data processing circuit 13 by the well-known NRZI system, and 16 is a second modulation for modulating the output data of the data processing circuit 14 by the well-known Bi-Phase system. Modulator as a means, 17 and 18 are modulators 15 and 16
The recording amplifier that amplifies the output of the
A recording current adjusting circuit connected to the recording heads 21, 21, 23, 24 are recording heads, and 25 is a magnetic tape.

Reference numerals 26, 27, 28 and 29 are reproduction heads, 30 and 31 are reproduction amplifiers for amplifying reproduction signals from the reproduction heads, 32 and 33 are equalizer circuits for ensuring the magnetic recording characteristics of the tape head, and 34 is the NRZI. A demodulator as a first demodulation means for demodulating data modulated by the method, a demodulator 35 as a second demodulation means for demodulating the data modulated by the Bi-Phase method,
Reference numerals 36 and 37 are data processing circuits which receive the outputs of the demodulators 34 and 35 and correct data errors due to dropout or the like generated in the tape head system.

Reference numeral 38 is a serial-parallel converter (hereinafter S →) for converting serial data from the data processing circuit 37 into parallel data.
Abbreviated as P converter), 39, 40, 41 are digital-analog converters (abbreviated as DA converter) as second conversion means,
42, 43, 44 are LPFs for interpolating the sampled signal, 45
Is an encoder circuit for quadrature two-phase modulation of the two color difference signals output from the LPFs 43 and 44 with color subcarriers to generate a carrier color signal, 46 is a mixing circuit for synthesizing the reproduced luminance signal and carrier color signal, 47 is an output terminal for the reproduced color video signal.

In the above configuration, the LPFs 6, 7 and 8 are selected according to the coding frequencies of the AD converters 9, 10 and 11 and the cutoff frequency is selected so as to prevent the return noise. The output signals of the color demodulation circuit 5 are (RY) signals and (BY) signals for convenience of description, but may be I signals and Q signals, as a matter of course. In this case, the modulation method of the encoder circuit 45 is configured to match that of the color demodulation circuit 5.

The data processing circuits 13, 14, 36 and 37 are configured to realize the code error correction according to the prior art described in the above-mentioned Television Society, Vol. 34, No. 3, pages 213 to 220. The implementation of the present invention is not limited by the difference in the code error correction method.

Reference numeral 48 denotes an input signal conversion circuit for inputting the luminance signal, the (RY) signal and the (BY) signal, sampling and converting into a digital signal, and outputting the luminance signal data and the chroma signal data. It is composed of converters 9, 10, 11 and a PS converter 12.

49 inputs the luminance signal data and the chroma signal data, and the luminance signal (RY) signal and (B-
Y) An output signal conversion circuit for outputting a signal, which is composed of the SP converter 38 and DA converters 39, 40, 41.

FIG. 2 is a block diagram showing an example of the input signal conversion circuit 48 of FIG. 1, and the same parts as those of FIG. In FIG. 2, 301 is a luminance signal input terminal, 302 is a (BY) signal input terminal, 303 is an (RY) signal input terminal, 304 is a luminance signal data output terminal, and 305 is a chroma signal. Data output terminal, 201 is a sampling clock signal generation circuit, 202 is a 1/2 divider circuit, 203 is a switch circuit, 204 is a 1/2 divider circuit, 205 is a 1/3 divider circuit,
206 is a delay circuit for 1 bit.

FIG. 3 is a block diagram showing an example of the sampling clock signal generation circuit 201. In FIG. 3, 311 is an input terminal of a reference subcarrier of the color subcarrier frequency sc, and 312 is an output of the sampling clock signal. A terminal, 214 is a phase detector, 215 is a voltage controlled oscillator (hereinafter abbreviated as VCO) having an oscillation frequency of about 4 sc, and 216 is a 1/4 frequency divider circuit. The signal input to the input terminal 311 is a burst signal that is normally included in the color video signal and transmitted, and the output terminal 312 outputs a clock signal of frequency 4sc.

FIG. 4 is a block diagram showing an example of the output signal conversion circuit 49 of FIG. 1, and the same parts as those in FIG. In FIG. 4, 306 is a reproduction luminance signal data input terminal, 307 is a reproduction chroma signal data input terminal, 308 is a luminance signal output terminal, 309 is a (BY) signal output terminal, and 310 is (R- Y) signal output terminal, 207 is a 3-bit delay circuit for matching the delay time with the chroma signal, 208 is a 1/6 frequency divider circuit 209 is a (BY) signal and (R-
Y) A delay circuit for adjusting the delay time of the signal, 210 is a clock signal generating circuit for converting the sampled data into an analog signal, and the output signal frequency is about 4
sc. 211 and 212 are latch circuits, and 213 is a switch circuit.

FIG. 5 is a signal waveform diagram of each part of FIGS. 2 and 4. In FIG. 5, a is a clock signal for sampling the luminance signal, which corresponds to the output signal of the 1/2 divider circuit 202 in FIG. 2, and its cycle 260 is from the above description. Is.

b indicates the sampling timing of the luminance signal, and Yn,
Y _{n + 1} represents the quantized data sampled, respectively. In the present invention, the number of quantized data is 8 bits as described above, and the luminance signal data output to the output terminal 304 in FIG. 2 is information of 8 bits for the sampling period.

c is a clock signal that samples the color difference signal, and
It corresponds to the output signal of the 1/3 frequency divider circuit 205 in the figure, and its cycle 261
From the above description Is.

d is the sampling timing of the (BY) signal, and e is (R-
Y) shows the sampling timing of the signal.

f is an output signal of the delay circuit 206, which is data delayed by 1 bit with respect to the sampling timing e.

g is a switching signal of the switch circuit 203, and its cycle 262
Is Is. The switch circuit 203 alternately selects the (BY) signal data d and the output signal data f in response to the switching signal g and outputs the selected data to the output terminal 305.

h is chroma signal data output to the output terminal 305, and is information of 6 bits for the sampling period.

i and l are output signals of the switch circuit 213 in FIG.
The switch circuit 213 distributes the signal of the chroma signal data input terminal 307 at the same cycle as the switching signal g described above. The signal of the input terminal 307 has the same timing as the chroma signal data h described above.

j is a latch circuit for latching the (RY) signal i
211, a latch circuit 2 for latching the (BY) signal m
There are 12 clock signals.

k is an output signal of the latch circuit 212, and is a signal obtained by latching the signal i for one cycle of the signal j.

The (BY) signal m is an output signal of the delay circuit 209 and is a signal in which the delay time with the (RY) signal i is corrected.

n is the output signal of the latch circuit 211, and the signal m is the signal j
The signal is latched for one cycle of. O is the delay circuit 207
Of the luminance signal data of the input terminal 306 and the (BY) signal and (RY) signal data. P is a clock signal of the delay circuit 207.

FIG. 6 is a waveform diagram for explaining the modulation method of the digital signal, 2A is a clock signal of frequency c, and the sampling period is 1 / c. 2B is a signal modulated by a so-called NRZ system, which is a binary signal representing "1" at "H" level and "0" at "L" level according to the cycle of the clock signal. 2C is a signal modulated by a method called the NRZI method, and is a binary signal that represents "1" when inverted according to the cycle of the clock signal and "0" when it is not inverted, which is almost the same as the NRZ method. It is a method. 2D is Bi
-Phase method modulated signal, which is encoded so that the data is always inverted within the period of the clock signal.

FIG. 7 is a diagram showing a frequency spectrum of a digital signal due to a difference in modulation method. In Fig. 7, the horizontal axis
3B represents frequency, and the vertical axis 3A represents relative level. T
Represents the period of the clock signal, Is. A curve 101 is a spectrum of a digital signal modulated by the NRZI system, and a curve 102 is a spectrum of a digital signal modulated by the Bi-Phase system.

As the signal modulated by the NRZI method can be easily inferred from FIG. 6, the inversion interval of the digital signal may be infinitely long, so it is a signal containing a lot of DC components and the inversion interval is the minimum. Since the cycle corresponds to one cycle of the clock frequency, the upper limit of the frequency spectrum matches the clock frequency c.

On the other hand, the signal modulated by the Bi-Phase method does not include a DC component because it is always inverted within one cycle of the clock frequency, and the upper limit value of the frequency spectrum is twice the clock frequency.

FIG. 8 is a diagram showing frequency spectra of luminance signal data and chroma signal data modulated by the modulation method in the embodiment of the present invention shown in FIG. In FIG. 1, the sampling interval of the luminance signal is T _Y and the sampling interval of the chroma signal is T _C, and T _C = 2T _Y (1) is selected. A curve 103 is the frequency spectrum of the luminance signal data modulated by the NRZI method, and the upper limit value is 1 / T _Y. curve
104 limit the frequency spectrum of the chroma signal data modulated by Bi-Phase scheme is a 2 / T _C, from the above equation (1) Is.

Therefore, in the embodiment of the present invention shown in FIG.
The frequency spectra of the luminance signal data and the chroma signal data recorded in 25 should be such that the spectra of the two hardly overlap in the low frequency band, that is, there is a large level difference between them and they overlap in the high frequency band. That is, the level difference between the two can be configured to be substantially zero.

On the other hand, it is known that when recording and reproducing a digital signal, a wider band is required than when recording and reproducing a normal analog signal.

It is known that with the current magnetic recording / reproducing technology, the wavelength of a signal recorded on a magnetic medium can be up to about 0.3 to 0.4 μm.

On the other hand, for example, VHS, which is known as the current home VTR
In the system, two magnetic heads are provided in a rotating cylinder, and the cylinder makes one rotation, whereby a color video signal for one frame can be recorded and reproduced. The relative speed between the magnetic tape and the magnetic head in this VHS system is 5.8 m / sec,
Therefore, if the recording wavelength is π = 0.3 μm, the recordable and reproducible frequency band _VHF is It is a degree.

In the embodiment of the present invention shown in FIG. 1, the required luminance signal band is usually 3 to 3.5 MHz, and the sampling clock frequency is at least 6 to 7 according to the well-known Nyquist theorem.
MHz or higher is required.

When sampling a color video signal, it is known to usually synchronize the clock frequency with the color subcarrier frequency.

In the embodiment of the present invention, for convenience, the sampling frequency of the luminance signal is
_CY is _CY = 2 _SC ( _SC is a color subcarrier frequency) and the number of quantized data is 8 bits in the explanation. However, the number of quantized data is not limited to this, and it depends on the sampling frequency and the number of quantized data. It goes without saying that it is possible to further widen the band by selecting the recording time.

From the above explanation, the frequency band when the luminance signal is modulated by the NRZI method with the clock frequency of 2 _SC and the quantized data number of 8 bits is 2 _SC x 8 bits = 2 x 3.58 MHz x 8 = 57.3 MHz. Is.

Therefore, in the above-mentioned VHS type domestic VTR, it is possible to record and reproduce the above-mentioned luminance signal data by doubling the relative speed between the magnetic tape and the magnetic head. Specifically, the rotational speed of the rotary cylinder may be tripled. On the other hand, the band of the chroma signal is usually 0.5 MHz to 1 MHz, and the sampling frequency is 1 MHz to 2 MHz or more.

In the embodiment of the present invention, for convenience, the sampling frequency of the chroma signal is The case where the number of quantized data is 6 bits will be described. Since the chroma signal data is two types of signals, that is, a (BY) signal and an (RY) signal, and the modulation method is the Bi-Phase method, the value obtained by multiplying the clock frequency by the number of bits is 4 Double the bandwidth required, Is.

It is necessary to record the chroma signal data at the same time as the above luminance signal data, and in the present invention, two magnetic heads capable of simultaneously recording and reproducing are arranged on the rotary cylinder.

FIG. 9 is a diagram showing the structure of a rotary head suitable for application to the device of the present invention. In FIG. 9, 21 and 22, 23 and 24 are heads capable of recording and reproducing at the same time, and they are mounted on the rotary cylinder 109 in close proximity to each other, and may have a structure in which the upper and lower sides are overlapped with each other. It is well known that they may be displaced in position and mounted in close proximity.

In the embodiment of the present invention, the luminance signal data is obtained by the heads 21 and 23,
The case where the heads 22 and 24 are arranged to record and reproduce the chroma signal data will be described, but it is also possible to arrange so that the heads 22 and 24 record and reproduce the luminance signal data and the heads 21 and 23 record and reproduce the chroma signal data. Is.

FIG. 10 is a view showing another structure of the magnetic head applied to the device of the present invention, in which four heads 21, 22, 23, 24 are attached to the rotary cylinder 109 at intervals of 90 degrees. In the rotating cylinder of this configuration, the head 21 and 23 are used for the luminance signal data, 22 and 24.
It is easy to understand that the chroma signal data is recorded / reproduced and the two heads out of the four heads are always in contact with the magnetic tape 25. Therefore, it is basically the same as the rotary cylinder in FIG. Although the heads 21 to 24 are used for both recording and reproduction, they may be separately provided for recording and reproduction as shown in FIG.

FIG. 11 is a diagram showing recording tracks formed on a magnetic tape when recording is performed by a conventional recording method using a conventional rotary head. The rotary cylinder is a standard household VT
Since it rotates at 3 times R and records simultaneously with 2 heads,
Information for one field of the color video signal is formed by six tracks.

In FIG. 11, reference numeral 105 denotes a luminance signal recording track, and 106 denotes a chroma signal recording track, which are alternately arranged on the magnetic tape 25. Reference numeral 116 denotes the width of the recording track, and 117 denotes the width of a non-signal portion, which is a so-called guard band, provided between the recording tracks.

As can be easily guessed from FIG. 11, a VTR that converts a color video signal into a digital signal and records / reproduces it, the recording / reproducing time is about 1/6 that of a normal home VTR.
Therefore, in order to lengthen the recording time, it is necessary to reduce the track width 116 and eliminate the guard band width 117 in FIG.

On the other hand, in a normal VTR, when the magnetic head on the rotating cylinder forms a recording track on the magnetic tape, the recording track is not linear due to mechanical accuracy constraints, and the so-called track bending Shape distortion occurs. Further, there is a deviation between the magnetic head and the recording track, which is called a tracking error caused by an electrical error.

Even if these occur, the width of the magnetic head should be 5-10 μm wider than the width of the recording track so that recording and playback can be performed normally.
It is generally known that the width is increased by about m. For this reason, in FIG. 11, when the guard band width 117 is eliminated, for example, the signal of the adjacent track is leaked and reproduced in addition to the signal of the track that is originally reproduced. Becomes It is well known that the magnitude of adjacent crosstalk interference is expressed by the following equation.

In the equation (2), D is the signal component of the main track, u is the magnitude of the crosstalk component from the adjacent track,
w is the width of the recording track, d is the difference between the recording track width and the track width of the reproducing head, is the difference in inclination between the recording head gap and the reproducing head gap, and is the recording wavelength.

In order to properly reproduce the main track signal, it is necessary to reduce the adjacent crosstalk interference to about -20 dB or less. For example, in FIG. 11, when the magnetic heads of the tracks 105 and 106 and the reproducing head have the same inclination of the gap, the guard band width 117 is eliminated, and the width of the reproducing head is widened by 5 μm with respect to the width w of the recording track. If you do
The recording track width for reducing the adjacent crosstalk interference to −20 dB or less can be obtained from the equation (2).

When this formula is rearranged and the recording track width w is obtained, it is as follows.

Therefore, even if the guard band width 117 is eliminated, the recording track width needs to be 50 μm, and 50 μm is required to record and reproduce the color video signal for one field.
× 6 = 300 μm is required.

Therefore, in the present invention, the required track width is reduced by making the inclination of the gap of the head for recording the adjacent tracks different and performing so-called azimuth recording.

FIG. 12 is a view showing recording tracks 105 and 106 formed on the magnetic tape 25 according to the present invention, and the same parts as those in FIG. 11 are designated by the same reference numerals. In FIG. 12, the width 116 of the recording track is about 10 μm. Track 105 with luminance signal data recorded and track 1 with chroma signal data recorded
The magnetic head formed with 06 is attached to the rotating cylinder 109 (FIGS. 9 and 10) so that the gaps have different inclinations.

FIG. 13 is a diagram showing the inclination of the gap between the recording heads 21 and 22 applied to the device of the present invention. In FIG. 13, 117 is a gap of the magnetic head 21 for recording the luminance signal data, 11
Reference numeral 8 indicates a gap of the magnetic head 22 for recording chroma signal data, and 107 and 108 indicate tilt angles of the gaps 117 and 118.

FIG. 14 is a diagram showing adjacent crosstalk interference when the recording data of the recording track of FIG. 12 is reproduced with the head configuration of FIG. This FIG. 14 shows that in the above equation (2), the recording track width w = 10 μm, the difference between the recording track width and the track width of the reproducing head d = 5 μm, and the relative speed υ = 5.
8 / sec × 3 = 17.4 m / sec, where the horizontal axis 9B represents frequency and the vertical axis 9A represents the relative value of the adjacent crosstalk to the main track signal.

In FIG. 14 described above, a curve 119 shows the case where the inclination angle of the gap of the magnetic head for recording / reproducing the main track and the adjacent track = 20 degrees, and a curve 121 shows the case where = 60 °. In the case of = 20 degrees, 120 indicates the amount of adjacent crosstalk in the approximately 30 MHz band, which is approximately -22 dB. On the other hand, the amount of adjacent crosstalk in the low frequency band is about −10 dB.

In the present invention, as described above with reference to FIG. 12, the tracks for recording the luminance signal data and the tracks for recording the chroma signal data are alternately formed on the magnetic tape, and the luminance signal is recorded as described in FIG. Since the frequency spectrums of data and chroma signal data are modulated by different methods such as NRZI method and Bi-Phase method, the frequency spectrums of both do not almost overlap in the low frequency band, and the amount of adjacent crosstalk between magnetic heads However, even if becomes as large as about -10 dB, the interference due to adjacent crosstalk causes almost no problem.

On the other hand, the high frequency band where the frequency spectra of the luminance signal data and the chroma signal data overlap with each other is the sampling period T _Y of the luminance signal data. The recording frequency is converted from the fact that the number of quantized data is 8 bits, × 8 28.6MHz or higher band. Therefore, the 14th
As shown in the figure, the amount of adjacent crosstalk in the band of 30 MHz or more is as long as the gap between the head recording the luminance signal data forming the tracks adjacent to each other and the head recording the chroma signal is about 20 degrees or more. It is below -20 dB and does not become an interfering signal.

Therefore, in the present invention, only 10 μm is required as the recording track width, and 10 μm × 6 = 60 μm is sufficient for recording / reproducing the color video signal for one field.

In the above description, the recording track width is set to 10 μm, but the present invention is not limited to this and may be appropriately selected in consideration of the recording time. Further, only the case where the adjacent tracks are formed by the luminance signal data and the chroma signal data has been described, but the essence of the present invention is (1) that the frequency spectra of the signals forming the adjacent tracks are modulated so as not to overlap, (2) The gap between the heads for recording / reproducing adjacent tracks has an inclination. For example, the present invention can be applied to a configuration in which a luminance signal and a chroma signal are converted into digital signals without being separated.

In addition, the NRZI method and Bi
Although it has been described as the -Phase method, any modulation method having different frequency spectrum bands occupied by each other may be used, and another modulation method described in the above-mentioned journal of the Television Society may be adopted.

FIG. 15 is a block diagram showing another embodiment of the present invention in which the same parts as those in FIG. 15 is different from FIG. 1 in that emphasis circuits 50, 51, 52 are provided before LPFs 6, 7, 8 and de-emphasis circuits 53, 54, 55 are provided after LPFs 42, 43, 44. That is.

FIG. 16 is a characteristic diagram showing the input / output characteristics of the emphasis circuit 50 with respect to the luminance signal. The horizontal axis 16B shows the frequency, and the vertical axis 16A shows the emphasis amount. Curves 245, 246, and 247 show the emphasis amounts when the input level of the luminance signal is 0 dB, −10 dB, and −20 dB, respectively.

FIG. 17 is a characteristic diagram showing the input / output characteristics of the de-emphasis circuit 53 with respect to the luminance signal. Horizontal axis 17B is frequency, vertical axis 1
7A indicates the amount of de-emphasis. Also, the curves 248,249,25
0 indicates that the input level of the luminance signal is 0 dB, -10 dB, -2, respectively.
The de-emphasis amount at 0 dB is shown.

The de-emphasis circuit 53 suppresses the quantization noise when the level of the input signal becomes small, and suppresses only the noise component by making the emphasis characteristic the inverse characteristic of the de-emphasis characteristic.

The emphasis characteristic is usually a characteristic for emphasizing the band of 100 KHz to 1 MHz or more, but is not limited to this and may be selected as an appropriate frequency from the noise component suppression effect. (B
-Y) signal and (RY) signal emphasis circuit 51,
The characteristics of 52 and the de-emphasis circuits 54 and 55 may be appropriately selected in consideration of the band of the chroma signal, and the characteristics of the emphasis circuits 51 and 52 need not be matched. However, the emphasis circuit 51 needs to have the inverse characteristic of the de-emphasis circuit 54, and the emphasis circuit 52 needs to have the inverse characteristic of the de-emphasis circuit 55.

Further, according to the configuration of FIG. 15, since quantization noise can be suppressed, it is possible to reduce the number of quantized data when converting into a digital signal. For example, in FIG. 1, the case where the luminance signal is quantized into 8 bits and the (BY) signal and the (RY) signal are quantized into 6 bits has been described, but in FIG. 15, it is reduced to 7 bits and 5 bits, respectively. It is also possible to do so.
In this case, the recording band of the digital signal can be reduced to about 7/8 and recording can be performed for a long time.

In FIG. 15, emphasis circuits 50, 51 and 52 are LPF6,
It can be easily understood that it is more advantageous to provide it in the preceding stage of 7, 8 in terms of the LPF out-of-band suppression characteristic, and the de-emphasis circuit
53,54,55 are also installed after LPF42,43,44.

〔The invention's effect〕

As is apparent from the above description, the digitally converted video signal is modulated so that adjacent tracks have different frequency spectrum signals, and the modulated signal is adjusted so that the azimuth angle difference is such that the tracks contact each other. Since it was configured to perform azimuth recording with the held head, adjacent crosstalk interference was prevented by modulating as described above in the low frequency band and by using azimuth recording as described above in the high frequency band. Can be reduced. Therefore, a guard band between adjacent tracks is unnecessary, the recording track width can be reduced, the economic efficiency of the recording tape can be significantly improved, and the recording time can be lengthened.

That is, when the design values such as the recording track width, the diameter of the rotating cylinder, and the tape feeding speed are selected as the numerical values of the above embodiment, the recording density is 5 to 6 times as high as that of the conventional magnetic recording / reproducing apparatus for digital video signals ( It is possible to improve the recording time).

Further, in order to improve the quality of the digitally converted video signal, the recording track width may be widened. Therefore, even if the recording track width is the same as the recording track of the conventional device, only the unnecessary portion of the guard band is recorded. Save time,
The effect that the recording density of about 2 times can be obtained is achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a magnetic recording / reproducing apparatus of the present invention, FIG. 2 is a block diagram of an input signal conversion circuit which is a constituent element of the apparatus of FIG. 1, and FIG. 3 is its input signal conversion circuit. FIG. 4 is a block diagram of a sampling clock signal generating circuit which is a constituent element of FIG. 4 is a block diagram of an output signal conversion circuit which is a constituent element of the apparatus shown in FIG. 1, and FIG. 5 is each circuit portion shown in FIGS. 2 and 4. FIG. 6 is a signal waveform diagram for explaining a digital signal modulation method, FIGS. 7 and 8 are diagrams for explaining a frequency spectrum of a recording signal, and FIGS. 9 and 10 are for a magnetic head. FIG. 11 is a diagram for explaining the arrangement, FIG. 11 is a configuration diagram of recording tracks by a conventional magnetic recording / reproducing apparatus, FIG. 12 is a configuration diagram of recording tracks by the magnetic recording / reproducing apparatus of the present invention, and FIG. 13 is a magnetic head of the apparatus of the present invention. Figure explaining the installation state of
FIG. 14 is a diagram showing the level of adjacent crosstalk interference, FIG. 15 is a block diagram showing a second embodiment of the magnetic recording / reproducing apparatus of the present invention, and FIGS. 16 and 17 are diagrams explaining the second embodiment. is there. 9, 10, 11 ... First conversion means (AD converter) 13 ... First modulation means (NRZI type modulator 14 ... Second modulation means (Bi-Phase type modulator) 21 ... 24, 26 to 29 ...... Magnetic head 25 ...... Magnetic tape 34 ...... First demodulation means (NRZI system demodulated signal demodulator) 35 ...... Second demodulation means (Bi-Phase system demodulated signal demodulation) 39,40,41 …… Second conversion means (DA converter)

Claims (4)

[Claims] 1. A converting means for converting an analog video signal into a digital video signal, first and second modulating means for modulating the digital video signal so as to obtain signals having different frequency spectra, respectively. A plurality of magnetic heads mounted on the rotating cylinder with an azimuth angle difference for recording the signals modulated by the second modulating means on the magnetic tape so that adjacent recording tracks contact each other. Magnetic recording device for digital video signals. 2. The digital video signal according to claim 1, wherein the first modulating means is an NRZI modulating method and the second modulating means is a Bi-Phase modulating method. Magnetic recording device. 3. A first converting means for converting an analog video signal into a digital video signal, and a first and a second modulating means for modulating the digital video signal so as to obtain signals having different frequency spectra, respectively. A plurality of magnetic heads mounted on a rotary cylinder with an azimuth angle difference for recording the signals modulated by the first and second modulating means on a magnetic tape so that adjacent recording tracks are in contact with each other; A first demodulation means for demodulating a reproduction signal from the magnetic tape modulated by the modulation means of
Second demodulating means for demodulating the reproduced signal from the magnetic tape modulated by the modulating means, and second digital demodulating means for converting the digital video signal demodulated by the first and second demodulating means into an analog video signal. And a magnetic recording / reproducing apparatus for digital video signals. 4. A magnetic recording / reproducing apparatus for a digital video signal according to claim 3, wherein the magnetic head is also used for recording and reproducing.